I have little doubt we'll eventually see all this bonus content in print, but it won't happen for some time. It's going to take months just to write it all, and when the time comes I don't think Rich is just going to stick all the PDFs together and call it a day; he'll want to come up with more bonus stuff for the book. He's also got bonus content for Book 5 to write. The same reasoning for Book 5 applies to any bonus book: Rich doesn't want to take money for a goal for which he has no firm details, especially about when it will come out.
Incidentally, in honour of the spectacularly successful fundraiser, my proposed title is, "A Fist Full of GP".
In other news, the graph seems to be fairly closely following a quadratic curve (minus a couple of outliers around $250k). If it continues to follow the curve, it will finish at around $770k, give or take $10k, let's say.